recompressing audio but not the video produces file which will not play smoothly Matthew Shaver <yumecorp[ at ]newsgroup.nospam> 5/12/2007 1:01:19 AM I have written a program which takes a WMV file and copies the video stream in its compressed form but recompresses the audio stream to a lossless format. This produces an output file where sometimes the video is very jerky or where sometimes the audio is intermittent. If I change this program to also recompress the video back to its original format I get a file which plays OK but the video quality has been degraded. My theory is that the change in audio format produces a change in size of the audio samples. And in the case where the video stream is not being recompressed the resulting file does not have the proper interleaving of the audio and video data for smooth playback. Does this theory sound like what is happening? Is it just required that if one stream is recompressed that they all need to be recompressed? Or is there anything I can do at the WMF API level to make this kind of conversion produce a usable output? Thanks, Matt.

Re: recompressing audio but not the video produces file which will not play smoothly sasha <abc[ at ]fox.net> 5/12/2007 5:03:23 PM Matthew Shaver wrote: [snip] [Quoted Text] > Is it just required that if one stream is recompressed that they all > need to be recompressed? > > Or is there anything I can do at the WMF API level to make this kind of > conversion produce a usable output? > I came across the following situation: I'm transcoding a file. Only video needs to be re-compressed. So I asked reader to give me compressed audio and uncompressed video. What I observed was that audio was running ahead of the video, i.e. the reader was constantly giving me audio samples, but not all video samples. Asking the reader for both streams uncompressed resolved the problem.